Combine cubed steak, mesquite peppercorn seasoning and beer in a resealable bag. Seal bag, toss to combine and marinate at least 2 hours or overnight.
Combine melted butter, Garlic Junkie seasoning and pepper in a glass measuring cup.
Place vegetables in a large bowl and pour half of the butter mixture over top. Gently toss to coat.
To assemble kabobs, alternately thread steak and vegetables onto skewer in a decorative fashion; discard beef marinade. For the MEATER thermometer, assemble one kebob with at least 3 cubes of beef side by side. Insert the thermometer through all 3 pieces of steak, parallel with the skewer.
Preheat grill to medium-high. When the grill is hot, lightly oil the grates and place the kebobs on the grill. Cook, turning occasionally, about 10-12 minutes, basting kabobs with remaining garlic butter every few minutes. Kabobs are done when vegetables are tender and lightly charred, and meat is cooked to desired doneness as indicated by MEATER thermometer. Serve warm.