Start by preheating your oven to 350°F (177°C). Line a large baking sheet with foil or parchment and spray lightly with nonstick spray. This keeps everything from sticking and makes cleanup much easier.
In a large bowl, combine the potatoes and Brussels sprouts with olive oil, steakhouse seasoning, lemon pepper, and garlic salt. Toss well to coat. Spread the veggies over half the baking sheet, then squeeze fresh lemon juice over them for extra brightness.
Pound the chicken breasts to an even thickness and place them on the other half of the sheet. Drizzle with olive oil, then season both sides with steakhouse seasoning, lemon pepper, and garlic salt. Add a few lemon slices on top if you want more citrus aroma.
Bake for 30–35 minutes until the chicken is cooked through and the potatoes are fork-tender. Let the dish rest for a couple of minutes so everything stays juicy before serving.