Cut each bok choy in half lengthwise. Rinse under cold running water, spreading outside layer of leaves to wash away dirt. Pat dry with paper towels. Discard stems from mushrooms. Wipe mushroom caps with damp paper towels to remove grit, then slice in half.
Heat oil in a large wide frying pan or wok over medium-high. Add garlic, mushrooms and bamboo shoots. Stir-fry until mushrooms start to soften, 2 to 3 min. If pan gets too hot, reduce heat to medium. Add bok choy. Stir often until bok choy stalks are tender-crisp, 4 to 5 more min. Drizzle with oyster sauce until evenly mixed. Remove to a platter.
Nutrition (per serving)
The bok choy looks elegant in this quick stir-fry with shiitakes, bamboo shoots and oyster sauce.