Les McDonald, Jr. was born in Victoria, Texas, in 1943 and grew up in Port O'Connor on the Texas Gulf Coast, surrounded by the wildlife and open water that would shape his life's work. He earned a B.S. in Commercial Art with a minor in photography from Sam Houston State College and spent the next twenty years working in advertising in Houston, eventually owning his own agency. 

In 1986, Les left advertising to become a full-time fine artist. He had started in oils but soon switched permanently to watercolor, a medium he said allowed him to experiment more than any other. "With watercolors," he explained, "I like to paint, drool, scratch, dab, mop, salt, and incorporate a wide variety of techniques" — an approach that became the foundation of the highly detailed, realistic style he was known for. People frequently mistook his paintings for photographs. As one collector put it, when he looked at a Les McDonald painting he knew that Les had been there, because the scene was captured so realistically. Another described being able to feel the salt air on his neck looking at one of Les's paintings of birds hitching a ride on the Bolivar ferry. 

Les's travels took him from Alaska to Argentina in search of subjects, though his deepest and most consistent inspiration remained close to home: the birds, landscapes, seascapes, still life, and sporting art of the Texas coast. Texas artists John Cowan and Herb Booth were early influences on his realist style. His work was exhibited nationally, including at the Waterfowl Festival in Easton, Maryland; the Southeastern Wildlife Exhibition in South Carolina; the National Wildlife Exhibition in Kansas City; Nature Works in Tulsa, Oklahoma; the Florida Wildlife Expo in Orlando; and the Rockport Art Festival in Texas. He was also a longtime supporter of conservation organizations including Ducks Unlimited, the Coastal Conservation Association, Texas Quail Coalition, Quail Unlimited, and Waterfowl U.S.A. 

Les joined the Watercolor Art Society-Houston (WAS-H) in 1986 and began entering its competitions in the early 1990s, eventually being accepted into nine International Shows and numerous Membership Shows. He achieved Elite Signature status at WAS-H in 2013, and went on to hold signature memberships in the Society of Watercolor Artists, the Southwestern Watercolor Society, and the Texas Watercolor Society. In 2024, the American Watercolor Society awarded him national Signature status. His paintings won repeated recognition over the years, including first place for "Dining Out" in the 2021 WAS-H Membership Show, first place for "Lemons and Silver" in that November's monthly exhibit, a Merit award for "Farmer's Market" in the 2021 International Show, the Memorial of Past Members Award from the Southwestern Watercolor Society for "Fire Up the Grill" in 2024, and Best of Show from the Houston Art Society in 2024. His work was featured in Splash magazine's best-of-watercolor editions in 2017, 2021, 2022, 2023, and 2025. 

Beginning in 2014, Les turned his attention to teaching, leading watercolor workshops at WAS-H for over a decade. Students remembered him for his patience, his deep knowledge of materials and methods, and his generosity in sharing technique — answering, again and again, the question he was most often asked: how he was able to paint with such extraordinary detail. He took particular delight in his students' accomplishments. 

Outside the studio, Les's greatest pleasures were the outdoors — hunting and fishing were where much of his inspiration for painting began. He lived and worked from his studio in Houston with his wife, Dianne, and continued showing in galleries along the Texas coast throughout his life.