Wrap tofu block in several layers of heavy-duty paper towels. Press with a heavy object for about 30 minutes to remove excess water. Remove paper towels, pat tofu dry, and cut into 1-inch cubes.
Combine hoisin sauce and next 3 ingredients in a small bowl; add tofu, tossing gently to coat.
Heat oil in a large nonstick skillet over medium-high heat. Add bok choy, garlic, and bell pepper; cook 3 to 4 minutes or until vegetables are crisp-tender. Reduce heat to low; add tofu mixture. Cook 2 minutes, or until tofu is thoroughly heated and vegetables are glazed.